I have a three yr old 1406 vortec headed flat top piston, mild can 355. It dies in gear, even with a 1500 rpm idle. Ran fine last year. I have fresh 93 octane gas in it. I tried adjusting the carb and noticed that I can turn the drivers side screw all the way in and out without any change in the idle, the passengers side screw works well. Am I right to assume that both screws should have an equal effect on the idle? Think I need to rebuild the carb? And the way I wanted to adjust the carb is to turn each screw individually until I have the highest idle, is that correct? Thanks for any help!